<!Doctype html>
<html>
<head>
    <meta charset='UTF-8'>
    <title>Document</title>
</head>
<body>

</body>
<script>
// 对象 {} []-数组 null
var arr = [1,2,3]
console.log(arr);
// 数组中的'键' => 下标

var arr = new Array()
console.log(arr);


var arr = []

var arr = new Array()


var arr = [1,2,3,4];
var arr = ['a','b','c','d'];
var arr = ['a',1,true,undefined,function(){}];

var arr = new Array(1,2,3);
console.log(arr);


var arr = [5]; // 有1个小空间，里面存了5
console.log(arr);

var arr = new Array(5) // 有5个空的小空间
console.log(arr);

var a = new Number(10)

</script>
</html>